Grafting polypropylene over hollow glass microspheres by reactive extrusion

Abstract

Hollow glass microspheres HGM are light, round, hollow, hydrophilic microspheres used to produce polyolefin composites with reduced density. To maintain mechanical strength, it is necessary to improve the adhesion between the polymer matrix and the microspheres, which is done by a compatibilizer. For polypropylene composites a maleic anhydride grafted polypropylene copolymer PP-g-MAH is employed. The melt mixing is done in a reactive extrusion when the maleic group of the compatibilizer reacts with hydroxyl groups present at the microspheres' surface, grafting a long PP chain. The aim of this work is to quantify the esterification grafting conversion and its efficiency during the reactive extrusion to the formation of PP/HGM composites compatibilized with PP-g-MAH. Techniques like TGA, FTIR and SEM were used to quantify the grafted PP content formed and the efficiency of the esterification reaction, which is mainly dependent of the compatibilizer concentration and reactive extrusion temperature.